Now ive personally never done a 16v
But I believe the rocker also holds the cams in as well
But im not 100% sure on that
As for cleaning yes small wire brushs will help
Sand paper will get really rough bits up quickly
You will probably need an etch primer to allow paint to stick
When I did the cover on my 16v.. I used Autsol.and a small wire brush and some wet and dry. It came up more or less chrome..
Autosol is used by bikers for cleaning chrome on engines
I get fed up with it and painted the full engine in ceramic black.